The role of environmental and spatial processes in structuring lake communities from bacteria to fish

We assessed the relative roles of local environmental conditions and dispersal on community structure in a landscape of lakes for the major trophic groups. We use taxonomic presence-absence and abundance data for bacteria, phytoplankton, zooplankton, and fish from 18 lakes in southern Quebec, Canada. The question of interest was whether communities composed of organisms with more limited dispersal abilities, because of size and life history (zooplankton and fish) would show a different effect of lake distribution than communities composed of good dispersers (bacteria and phytoplankton). We examine the variation in structure attributable to local environmental (i.e., lake chemical and physical variables) vs. dispersal predictors (i.e., overland and watercourse distances between lakes) using variation partitioning techniques. Overall, we show that less motile species (crustacean zooplankton and fish) are better predicted by spatial factors than by local environmental ones. Furthermore, we show that for zooplankton abundances, both overland and watercourse dispersal pathways are equally strong, though they may select for different components of the community, while for fish, only watercourses are relevant dispersal pathways. These results suggest that crustacean zooplankton and fish are more constrained by dispersal and therefore more likely to operate as a metacommunity than are bacteria and phytoplankton within this studied landscape.     

Zooplankton biodiversity and lake trophic state: explanations invoking resource abundance and distribution

While empirical studies linking biodiversity to local environmental gradients have emphasized the importance of lake trophic status (related to primary productivity), theoretical studies have implicated resource spatial heterogeneity and resource relative ratios as mechanisms behind these biodiversity patterns. To test the feasibility of these mechanisms in natural aquatic systems, the biodiversity of crustacean zooplankton communities along gradients of total phosphorus (TP) as well as the vertical heterogeneity and relative abundance of their phytoplankton resources were assessed in 18 lakes in Quebec, Canada. Zooplankton community richness was regressed against TP, the spatial distribution of phytoplankton spectral groups, and the relative biomass of spectral groups. Since species richness does not adequately capture ecological function and life history of different taxa, features which are important for mechanistic theories, relationships between zooplankton functional diversity (FD) and resource conditions were examined. Zooplankton species richness showed the previously established tendency to a unimodal relationship with TP, but functional diversity declined linearly over the same gradient. Changes in zooplankton functional diversity could be attributed to changes in both the spatial distribution and type of phytoplankton resource. In the studied lakes, spatial heterogeneity of phytoplankton groups declined with TP, even while biomass of all groups increased. Zooplankton functional diversity was positively related to increased heterogeneity in cyanobacteria spatial distribution. However, a smaller amount of variation in functional diversity was also positively related to the ratio of biomass in diatoms/chrysophytes to cyanobacteria. In all observed relationships, a greater variation of functional diversity than species richness measures was explained by measured factors, suggesting that functional measures of zooplankton communities will benefit ecological research attempting to identify mechanisms behind environmental gradients affecting diversity.     

Native fish diversity alters the effects of an invasive species on food webs

Aquatic communities have been altered by invasive species, with impacts on native biodiversity and ecosystem function. At the same time, native biodiversity may mitigate the effects of an invader. Common carp (Cyprinus carpio) is a ubiquitous, invasive fish species that strongly influences community and ecosystem processes. We used common carp to test whether the potential effects of an invasive species are altered across a range of species diversity in native communities. In mesocosms, treatments of zero, one, three, and six native fish species were used to represent the nested subset patterns observed in fish communities of lakes in Illinois, USA. The effect of the invader was tested across fish richness treatments by adding common carp to the native community and substituting native biomass with common carp. Native species and intraspecific effects reduced invader growth. The invader reduced native fish growth; however, the negative effect was minimized with increasing native richness. The zooplankton grazer community was modified by a top-down effect from the invader that increased the amount of phytoplankton. Neither the invader nor richness treatments influenced total phosphorus or community metabolism. Overall, the invader reduced resources for native species; and the effect scaled with how the invader was incorporated into the community. Higher native diversity mitigated the impact of the invader, confirming the need to consider biodiversity when predicting the impacts of invasive species.     

Is catchment productivity a useful predictor of taxa richness in lake plankton communities?

The influence of catchment variables on lake organisms is understudied. The terrestrial zone in the vicinity of lakes is, however, probably highly important for biota due to the effects on water chemistry and to various processes operating across ecosystem boundaries. We examined the relative importance of lake and catchment variables, as well as large-scale geographical factors, on the taxa richness of phyto- and zooplankton in 100 small lakes in Finland. In variation partitioning, the variability of phytoplankton richness was most strongly related to the effects of lake variables, the joint effects of lake and catchment variables, and the joint effects of all three groups of variables. Zooplankton richness, in turn, was most strongly related to the effects of lake and catchment variables and the joint effect of lake and catchment variables. The exact results of the variation partitioning depended on the catchment sizes considered in the regression models. Among lake variables, planktonic richness was strongly related to variables indicating productivity. Among catchment variables, the normalized difference vegetation index (NDVI), indicating catchment productivity, showed a relatively strong association with planktonic richness. These results provide evidence that catchment variables such as the NDVI may be efficient predictors of planktonic richness in small lakes. It is possible that individual lakes embedded in a highly productive landscape have higher taxa richness than solitary, potentially productive lakes because of the high influx of dispersing propagules from the regional pool. We also suggest that catchment variables may respond to environmental changes at different scales than the lake variables, and explicit consideration of catchment productivity would therefore be useful when planning research and monitoring programs for freshwater organisms.     

Effectiveness of terrestrial protected areas for conservation of lake fish communities

Freshwater protected areas are rare even though freshwater ecosystems are among the most imperiled in the world. Conservation actions within terrestrial protected areas (TPAs) such as development or resource extraction regulations may spill over to benefit freshwater ecosystems within their boundaries. Using data from 175 lakes across Ontario, Canada, we compared common indicators of fish‐assemblage status (i.e., species richness, Shannon diversity index, catch per unit effort, and normalized‐length size spectrum slopes) to evaluate whether TPAs benefit lake fish assemblages. Nearest neighbor cluster analysis was used to generate pairs of lakes: inside versus outside, inside versus bordering, and bordering versus outside TPAs based on lake characteristics. The diversity and abundance indicators did not differ significantly across comparisons, but normalized‐length size spectrum slopes (NLSS) were significantly steeper in lakes outside parks. The latter indicated assemblage differences (greater abundances of small‐bodied species) and less‐efficient energy transfer through the trophic levels of assemblages outside parks. Although not significantly different, pollution‐ and turbidity‐tolerant species were more abundant outside parks, whereas 3 of the 4 pollution‐intolerant species were more abundant within parks. Twenty‐one percent of the difference in slopes was related to higher total dissolved solids concentrations and angling pressure. Our results support the hypothesis that TPAs benefit lake fish assemblages and suggest that NLSS slopes are informative indicators for aquatic protected area evaluations because they represent compositional and functional aspects of communities.     

Lake of flies, or lake of fish? A trophic model of Lake Malawi

Ecosystem-focused models have, for the first time, become available for the combined demersal and pelagic components of a large tropical lake ecosystem, Lake Malawi. These provide the opportunity to explore continuing controversies over the production efficiencies and ecological functioning of large tropical lakes. In Lake Malawi these models can provide important insight to the effect of fishing on fish composition, and the potential competition that the lakefly Chaoborus edulis may have with fisheries production. A mass-balanced trophic model developed for the demersal fish community of the southern and western areas of Lake Malawi was integrated with an existing trophic model developed for the open-water pelagic. Input parameters for the demersal model were obtained from a survey of fish distributions, fish food consumption studies, and from additional published quantitative and qualitative information on the various biotic components of the community. The model was constructed using the Ecopath approach and software. The graphically presented demersal food web spanned four trophic levels and was based primarily on consumption of detritus, zooplankton and sedimented diatoms. Zooplankton was imported into the system at trophic levels three and four through fish predation on carnivorous and herbivorous copepods and Chaoborus larvae. It is proposed that the primary consumption of copepods was by fish migrating into the pelagic zone. Chaoborus larvae in the demersal were probably consumed near the lakebed as they conducted a daily migration from the pelagic to seek refuge in the sediments. This evidence for strong benthic-pelagic coupling provided the opportunity for linking the demersal model to the existing model for the pelagic community so producing the first model for the complete ecosystem. Energy fluxes through the resulting combined model demonstrated that the primary import of biomass to the demersal system was detritus of pelagic origin (72.1%) and pelagic zooplankton (10.6%). Only 15.8% of the biomass consumed within the demersal system was of demersal origin. Lakefly production is efficiently utilised by the lake fish community, and any attempt to improve fishery production through introduction of a non-native plantivorous fish species would have a negative impact on the stability and productivity of the lake ecosystem.     

Large-scale biodiversity patterns in freshwater phytoplankton

Our planet shows striking gradients in the species richness of plants and animals, from high biodiversity in the tropics to low biodiversity in polar and high-mountain regions. Recently, similar patterns have been described for some groups of microorganisms, but the large-scale biogeographical distribution of freshwater phytoplankton diversity is still largely unknown. We examined the species diversity of freshwater phytoplankton sampled from 540 lakes and reservoirs distributed across the continental United States and found strong latitudinal, longitudinal, and altitudinal gradients in phytoplankton biodiversity, demonstrating that microorganisms can show substantial geographic variation in biodiversity. Detailed analysis using structural equation models indicated that these large-scale biodiversity gradients in freshwater phytoplankton diversity were mainly driven by local environmental factors, although there were residual direct effects of latitude, longitude, and altitude as well. Specifically, we found that phytoplankton species richness was an increasing saturating function of lake chlorophyll a concentration, increased with lake surface area and possibly increased with water temperature, resembling effects of productivity, habitat area, and temperature on diversity patterns commonly observed for macroorganisms. In turn, these local environmental factors varied along latitudinal, longitudinal, and altitudinal gradients. These results imply that changes in land use or climate that affect these local environmental factors are likely to have major impacts on large-scale biodiversity patterns of freshwater phytoplankton.     

Analysis of the influence of substrate variables on coral reef fish communities

A simple field technique to obtain a gross estimate of the surface area of a quadrat on a coral reef is described. This measure, termed the substrate rugosity index, was determined, in conjunction with two other substrate variables (vertical relief and coral species richness), in a series of 4 quadrats (10 to 40 m depth) along 4 transects. The mean substrate rugosity and vertical relief of a quadrat were highly correlated. A correlation analysis was made of the substrate variables and several reef fish community parameters (species richness, number of fishes and diversity). Species richness was highly correlated with substrate rugosity. This relationship was tested in two experimental quadrats and the results were generally in accord with those predicted. Stratification of the fish communities by body size revealed that the correlation with substrate rugosity was scale-dependent. The fish community parameters were poorly correlated with percentage substrate cover by corals (ramose and glomerate) and by sand. A significant area effect was determined for two species of sand-dwelling goby.     

Forecasting the Spread of Invasive Rainbow Smelt in the Laurentian Great Lakes Region of North America

Abstract:  Rainbow smelt ( Osmerus mordax ) have invaded many North American lakes, often resulting in the extirpation of native fish populations. Yet, their invasion is incipient and provides the rationale for identifying ecosystems likely to be invaded and where management and prevention efforts should be focused. To predict smelt presence and absence, we constructed a classification-tree model based on habitat data from 354 lakes in the native range for smelt in southern Maine. Maximum lake depth, lake area, and Secchi depth (surrogate measure of lake productivity) were the most important predictors. We then used our model to identify lakes vulnerable to invasion in three regions outside the smelt's native range: northern Maine (52 of 244 lakes in the non-native range), Ontario (4447 of 8110), and Wisconsin (553 of 5164). We further identified a subset of lakes with a strong potential for impact (potential–impact lakes) based on the presence of fish species that are affected by rainbow smelt. Ninety-four percent of vulnerable lakes in the non-native range in Maine are also potential–impact lakes, as are 94% and 58% of Ontario and Wisconsin's vulnerable lakes, respectively. Our modeling approach can be applied to other invaders and regions to identify invasion-prone ecosystems, thus aiding in the management of invasive species and the efficient allocation of invasive species mitigation and prevention resources.     

Trajectories of zooplankton recovery in the Little Rock Lake whole-lake acidification experiment.

Understanding the factors that affect biological recovery from environmental stressors such as acidification is an important challenge in ecology. Here we report on zooplankton community recovery following the experimental acidification of Little Rock Lake, Wisconsin, USA. One decade following cessation of acid additions to the northern basin of Little Rock Lake (LRL), recovery of the zooplankton community was complete. Approximately 40% of zooplankton species in the lake exhibited a recovery lag in which biological recovery to reference basin levels was delayed by 1-6 yr after pH recovered to the level at which the species originally responded. Delays in recovery such as those we observed in LRL may be attributable to "biological resistance" wherein establishment of viable populations of key acid-sensitive species following water quality improvements is prevented by other components of the community that thrived during acidification. Indeed, we observed that the recovery of species that thrived during acidification tended to precede recovery of species that declined during acidification. In addition, correspondence analysis indicated that the zooplankton community followed different pathways during acidification and recovery, suggesting that there is substantial hysteresis in zooplankton recovery from acidification. By providing an example of a relatively rapid recovery from short-term acidification, zooplankton community recovery from experimental acidification in LRL generally reinforces the positive outlook for recovery reported for other acidified lakes.     

Fish Faunas of the African Great Lakes: Origins, Diversity, and Vulnerability

The largest African Great Lakes, Tanganyika, Malawi, and Victoria, which have the richest lacustrine fish faunas of any of the world's lakes, provide a unique comparative series for studies of evolutionary mechanisms, community ecology, and fish behavior. Their colorful littoral fishes are also known to aquarists worldwide. This paper examines the origins of their fish diversity, looking at the history of the lakes, colonization from river systems, and evolution of endemic faunas within each lake. All three lakes support fisheries of great socioeconomic importance for the rapidly rising human populations. The paper also examines the vulnerability of the faunas to fishing pressures and introductions of exotic species. In Malawi and Victoria, bottom-trawling has altered the cichlid species composition. The loss of an estimated 200 taxa of endemic cichlid species from Lake Victoria's fauna, following introductions of exotic fishes (tilapias and predatory centropomid Lates ) 40 years ago, stresses the need to protect the unique fish faunas in Lakes Tanganyika and Malawi.     

Seasonal variation and diversity of rotifers in Ehoma lake, Nigeria

The zooplankton and physicochemistry of Ehoma lake were studied from March 2005 to August 2006 in order to evaluate seasonal trend in species composition and abundance in relation to water quality. Forty two (42) species of rotifers dominated by Keratella tropica tropica were encountered. Species richness declined by nearly 50% from dry season values during the rainy season. Species richness was higher in the littoral zone during the dry season, the reverse was the case during the rainy season. Species abundance followed similar trend as species richness. Abundance was closely associated with dissolved oxygen, biological oxygen demand and width of the lake and these in turn varied significantly between seasons. Shannon-Weaver diversity varied from 2.2 to 3.8 bit ind(-1) and significantly between seasons (p<0.05). Anuraeopsis navicula navicula and Euchlanis dilatata dilatata Ehrenbreg were the only species gained during the flood periods.     

深圳湾浮游动物的群落结构及季节变化

2008年2月、5月、8月和11月分别对深圳湾浮游动物进行了周年的季节调查,结果共检出浮游动物38种和浮游幼体13类,其中原生动物2种,腔肠动物4种,介形类1种,桡足类22种,软甲类3种,毛颚类3种,被囊类1种,多毛类2种,浮游幼体（包括仔鱼）13类。年均丰度和生物量分别为406.7 ind.m-3和764.0 mg.m-3,高峰均位于夏季,低谷分别位于冬、春季。种类数（包括浮游幼虫）秋季最多为43种,夏季次之为30种,冬季最少仅23种。主要优势种为太平洋纺锤水蚤Acartia pacifica、刺尾纺锤水蚤Acartia spinicauda、短角长腹剑水蚤Oithona brevicornis、双生水母Diphyes chamissonis、卡玛拉水母Malagazzia carolinae、蔓足类幼体和桡足幼体等。多样性指数和均匀度年均值分别为2.568和0.526。回归分析表明浮游动物丰度和生物量与各环境因子之间存在明显的相关性,但有季节变化。     

Aquatic plant community invasibility and scale-dependent patterns in native and invasive species richness

Invasive species richness often is negatively correlated with native species richness at the small spatial scale of sampling plots, but positively correlated in larger areas. The pattern at small scales has been interpreted as evidence that native plants can competitively exclude invasive species. Large-scale patterns have been understood to result from environmental heterogeneity, among other causes. We investigated species richness patterns among submerged and floating-leaved aquatic plants (87 native species and eight invasives) in 103 temperate lakes in Connecticut (northeastern USA) and found neither a consistently negative relationship at small (3-m2) scales, nor a positive relationship at large scales. Native species richness at sampling locations was uncorrelated with invasive species richness in 37 of the 60 lakes where invasive plants occurred; richness was negatively correlated in 16 lakes and positively correlated in seven. No correlation between native and invasive species richness was found at larger spatial scales (whole lakes and counties). Increases in richness with area were uncorrelated with abiotic heterogeneity. Logistic regression showed that the probability of occurrence of five invasive species increased in sampling locations (3 m2, n = 2980 samples) where native plants occurred, indicating that native plant species richness provided no resistance against invasion. However, the probability of three invasive species' occurrence declined as native plant density increased, indicating that density, if not species richness, provided some resistance with these species. Density had no effect on occurrence of three other invasive species. Based on these results, native species may resist invasion at small spatial scales only in communities where density is high (i.e., in communities where competition among individuals contributes to community structure). Most hydrophyte communities, however, appear to be maintained in a nonequilibrial condition by stress and/or disturbance. Therefore, most aquatic plant communities in temperate lakes are likely to be vulnerable to invasion.     

湖北省湖泊大型底栖动物群落结构及水质生物学评价

大型底栖动物是湖泊生态系统的重要生物类群,在生态系统物质循环和能量流动中起着重要作用。底栖动物具有生命周期长、迁移能力较弱、对环境变化反应敏感等特点,可有效指示湖泊生态系统的健康状况。湖北省是我国淡水湖泊分布最密集的区域之一,湖泊总面积为3025 km2。近年来,伴随着工农业、养殖业及城市化的快速发展,富营养化已成为本地区湖泊面临的一个主要环境问题,并可能直接影响大型底栖动物的群落结构。目前关于本地区湖泊大型底栖动物群落的研究还较少,为此本研究对湖北省27个浅水湖泊底栖动物进行了调查,并对水质状况进行生物学评价。共采集到底栖动物40种,隶属于4门7纲18科,其中寡毛类5种,摇蚊幼虫16种,软体动物双壳类4种、腹足类8种。霍甫水丝蚓（Limnodrilus hoffmeisteri）、苏氏尾鳃蚓（Branchiura sowerbyi）、花翅前突摇蚊（Procladius choreus）、中国长足摇蚊（Tanypus chinensis）、多巴小摇蚊（Microchironomus tabarui）及铜锈环棱螺（Bellamya aeruginosa）是本地区湖泊最常见的种类。所调查湖泊底栖动物平均密度为32~1243 ind·m-2,其中12个湖泊密度低于200 ind·m-2,摇蚊幼虫和寡毛类对密度的贡献较大,以摇蚊幼虫占优势的湖泊有19个。底栖动物平均生物量为0.034~460.7 g·m-2,生物量低于50 g·m-2的湖泊数量最多（19个）,软体动物占优势的湖泊有16个,摇蚊幼虫和寡毛类占优势的湖泊数量共11个。各湖泊底栖动物物种数为3~14种,Margalef指数为0.71~2.33,Simpson指数为0.69~0.85,Shannon-Wiener为0.78~2.13,Spearman相关性分析结果显示物种丰富度和三种多样性指数与湖泊面积呈显著正相关。BI（Hilsenhoff生物指数）评价结果显示共11个湖泊为一般和轻度污染（6.01~7.44）,中度污染湖泊数量为13个（7.57~8.47）,长湖（8.52）、上津湖（8.65）和玉湖（8.50）处于重污染状态。     

Bird metacommunities in temperate South American forest: vegetation structure, area, and climate effects

Spatial structure in metacommunities and their relationships to environmental gradients have been linked to opposing theories of community assembly. In particular, while the species sorting hypothesis predicts strong environmental influences, the neutral theory, the mass effect, and the patch dynamics frameworks all predict differing degrees of spatial structure resulting from dispersal and competition limitations. Here we study the relative influence of environmental gradients and spatial structure in bird assemblages of the Chilean temperate forest. We carried out bird and vegetation surveys in South American temperate forests at 147 points located in nine different protected areas in central Chile, and collected meteorological and productivity data for these localities. Species composition dissimilarities between sites were calculated, as well as three indices of bird local diversity: observed species richness, Chao estimate of richness, and Shannon diversity. A stepwise multiple regression and partial regression analyses were used to select a small number of environmental factors that predicted bird species diversity. Although diversity indices were spatially autocorrelated, environmental factors were sufficient to account for this autocorrelation. Moreover, community dissimilarities were not significantly related to distance between sites. We then tested a multivariate hypothesis about climate, vegetation, and avian diversity interactions using a structural equation modeling (SEM) approach. The SEM showed that climate and area of fragments have important indirect effects on avian diversity, mediated through changes in vegetation structure. Given the scale of this study, the metacommunity framework provides useful insights into the mechanisms driving bird assemblages in this region. Taken together, the weak spatial structure of community composition and diversity, as well as the strong environmental effects on bird diversity, support the interpretation that species sorting has a predominant role in structuring avian assemblages in the region.     

Habitat biodiversity as a determinant of fish community structure on coral reefs

Increased habitat diversity is often predicted to promote the diversity of animal communities because a greater variety of habitats increases the opportunities for species to specialize on different resources and coexist. Although positive correlations between the diversities of habitat and associated animals are often observed, the underlying mechanisms are only now starting to emerge, and none have been tested specifically in the marine environment. Scleractinian corals constitute the primary habitat-forming organisms on coral reefs and, as such, play an important role in structuring associated reef fish communities. Using the same field experimental design in two geographic localities differing in regional fish species composition, we tested the effects of coral species richness and composition on the diversity, abundance, and structure of the local fish community. Richness of coral species overall had a positive effect on fish species richness but had no effect on total fish abundance or evenness. At both localities, certain individual coral species supported similar levels of fish diversity and abundance as the high coral richness treatments, suggesting that particular coral species are disproportionately important in promoting high local fish diversity. Furthermore, in both localities, different microhabitats (coral species) supported very different fish communities, indicating that most reef fish species distinguish habitat at the level of coral species. Fish communities colonizing treatments of higher coral species richness represented a combination of those inhabiting the constituent coral species. These findings suggest that mechanisms underlying habitat-animal interaction in the terrestrial environment also apply to marine systems and highlight the importance of coral diversity to local fish diversity. The loss of particular key coral species is likely to have a disproportionate impact on the biodiversity of associated fish communities.     

Plankton biodiversity along a gradient of productivity and its mediation by macrophytes

We studied the effect of aquatic vegetation on the process of species sorting and community assembly of three functional groups of plankton organisms (phytoplankton, seston-feeding zooplankton, and substrate-dwelling zooplankton) along a primary productivity gradient. We performed an outdoor cattle tank experiment (n = 60) making an orthogonal combination of a primary productivity gradient (four nutrient addition levels: 0, 10, 100, and 1000 microg P/L; N/P ratio: 16) with a vegetation gradient (no macrophytes, artificial macrophytes, and real Elodea nuttallii). We used artificial plants to evaluate the mere effects of plant physical structure independently from other plant effects, such as competition for nutrients or allelopathy. The tanks were inoculated with species-rich mixtures of phytoplankton and zooplankton. Both productivity and macrophytes affected community structure and diversity of the three functional groups. Taxon richness declined with increasing plankton productivity in each functional group according to a nested subset pattern. We found no evidence for unimodal diversity-productivity relationships. The proportional abundance of Daphnia and of colonial Scenedesmus increased strongly with productivity. GLM analyses suggest that the decline in richness of seston feeders was due to competitive exclusion by Daphnia at high productivity. The decline in richness of phytoplankton was probably caused by high Daphnia grazing. However, partial analyses indicate that these explanations do not entirely explain the patterns. Possibly, environmental deterioration associated with high productivity (e.g., high pH) was also responsible for the observed richness decline. Macrophytes had positive effects on the taxon richness of all three functional plankton groups and interacted with the initial productivity gradient in determining their communities. Macrophytes affected the composition and diversity of the three functional groups both by their physical structure and through other mechanisms. Part of the macrophyte effect may be indirect via a reduction of phytoplankton production. Our results also indirectly suggest that the often reported unimodal relationship between primary productivity and diversity in nature may be partially mediated by the tendency of submerged macrophytes to be most abundant at intermediate productivity levels.     

Species dispersal rates alter diversity and ecosystem stability in pond metacommunities

Metacommunity theory suggests that relationships between diversity and ecosystem stability can be determined by the rate of species dispersal among local communities. The predicted relationships, however, may depend upon the relative strength of local environmental processes and disturbance. Here we evaluate the role of dispersal frequency and local predation perturbations in affecting patterns of diversity and stability in pond plankton metacommunities. Pond metacommunities were composed of three mesocosm communities: one of the three communities maintained constant "press" predation from a selective predator, bluegill sunfish (Lepomis macrochirus); the second community maintained "press" conditions without predation; and the third community experienced recurrent "pulsed" predation from bluegill sunfish. The triads of pond communities were connected at either no, low (0.7%/d), or high (20%/d) planktonic dispersal. Richness and composition of zooplankton and stability of plankton biomass and ecosystem productivity were measured at local and regional spatial scales. Dispersal significantly affected diversity such that local and regional biotas at the low dispersal rate maintained the greatest number of species. The unimodal local dispersal-diversity relationship was predator-dependent, however, as selective press predation excluded species regardless of dispersal. Further, there was no effect of dispersal on beta diversity because predation generated local conditions that selected for distinct community assemblages. Spatial and temporal ecosystem stability responded to dispersal frequency but not predation. Low dispersal destabilized the spatial stability of producer biomass but stabilized temporal ecosystem productivity. The results indicate that selective predation can prevent species augmentation from mass effects but has no apparent influence on stability. Dispersal rates, in contrast, can have significant effects on both species diversity and ecosystem stability at multiple spatial scales in metacommunities.